1. Field of the Invention
The present invention relates to a substrate sheet material for a semiconductor device and manufacturing method thereof and a manufacturing method of a semiconductor device using the substrate sheet material and, more particularly, to a technique effective to formation of a semiconductor device referred to as a ball grid array (BGA) or a land grid array (LGA).
2. Description of the Related Art
With miniaturization and speeding-up of electronic equipments, further miniaturization and higher densification are required for semiconductor devices applied to the electronic equipments.
In order to satisfy such requirements, semiconductor devices such as a ball grid array (BGA) or a land grid array (LGA) are used. Such a semiconductor device of a BGA type or a LGA type uses a substrate (a tape substrate or a printed board) that is made of polyimede or glass-epoxy. The substrate has a wiring layer on a surface thereof or inside thereof, and electrodes are formed on the surface. A semiconductor chip (semiconductor element) is mounted on the substrate, and electrodes of the semiconductor chip are electrically connected to the wiring/electrodes of the substrate. The semiconductor chip is encapsulated by a resin or other cap materials. Ball-like terminals or land-like terminals for external connection are provided on the electrodes. Japanese Laid-Open Patent Application No. 2000-12745 discloses a semiconductor device having the above-mentioned structure.
There is a demand for cost reduction with respect to the semiconductor devices of a BGA type or a LGA type. As one of measures for satisfying such a demand, it has been attempted to increase efficiency of the manufacturing method of the semiconductor devices after formation of the substrate.
That is, the above-mentioned substrate uses a polyimide sheet or a glass-epoxy sheet as a base material (blank material), the base material having a electrically conductive layer such as a copper (Cu) layer formed on at least one of main surfaces thereof so that the substrate is constituted as a resin substrate having a single layer structure or, if needed, a multi-layer structure in which wiring layers are provided between layers according to a semiconductor element mounted thereon.
At this time, the substrate (blank material) is prepared as a sheet-like material having a large area so as to form a substrate sheet material in which many substrates are formed, thereby, increasing a number of substrates, that is, a number of semiconductor chips mounted thereon so as to increase a number of semiconductor devices formed in a single process.
The plurality of substrates formed in the substrate sheet material are separated with the resin material which covers the semiconductor chips mounted on the substrates concerned after the above-mentioned terminals for external connection are arranged.
FIG. 1 shows a conventional manufacturing process from production of the substrates to production of the semiconductor devices.
First, a blank material 1, which is made of a resin sheet and turned into a material of substrates, is prepared. The blank material 1 has an area required for forming a desired plurality of substrates collectively.
Next, wiring corresponding to the plurality of substrates are performed on the blank material 1. In the example shown in FIG. 1, three substrate sheet materials 2 are formed from the blank material, and wirings corresponding to the plurality of substrate 3 are formed in each of the substrate sheet materials 2.
In the wiring process, a well-known technique in this field is used. That is, through holes are formed in the blank material 1, and copper (Cu) plating is applied to both sides of the blank material 1. If the blank material 1 has an electrically conductive layer such as copper (Cu) previously formed on a resin substrate, the electrically conductive material is used. Then, a resist is provided on the copper plating so as to perform photoetching to form the cupper plating into a predetermined pattern. Thereafter, nickel and gold plating is applied onto the copper plating, and the wiring process is completed.
After completion of the wiring process, the blank material 1 is cut and separated into the substrate sheet materials 2. Each of the substrate sheet materials 2 is in the form of a strip sheet in which a plurality of substrates are formed consecutively so as to facilitate handling in a subsequent process of manufacturing semiconductor devices. The strip-like substrate sheet materials 2 are supplied to an assembling process of semiconductor devices.
The substrates are formed by being arranged in two rows in the substrate sheet material 2 shown in FIG. 1.
In the semiconductor assembling process, semiconductor chips are mounted to all the substrates 3 formed in the single substrate sheet material 2, and the semiconductor chips are collectively resin-molded and finally individualized so as to efficiently form semiconductor devices.
If a substrate sheet material having a large area is resin-molded at one time, a warp may be generated in the substrate sheet material since a thermal expansion rates are different between the substrate sheet material 2 and the mold resin. In order to prevent generation of such a warp, there is a case in which a plurality of concaves (grooves) are provided on the surface of the resin mold. Such a structure is disclosed, for example, in Japanese Laid-Open Patent Application No. 2002-110718.
However, according to this approach, a mechanical strength is reduced since the grooves of the concaves must be made considerably deep, and destruction may occur during processes after the resin molding and after being separated into individual semiconductor devices. Moreover, there also is a problem in that it is difficult to provide a stamp on a surface of the molded resin.
As mentioned above, when forming semiconductor devices by forming a plurality of substrates in a single substrate sheet material and mounting a semiconductor chip on each portion corresponding to a substrate and thereafter resin-molding the semiconductor chips collectively, the semiconductor devices can be formed more efficiently by forming many more substrates 3 in a single substrate sheet material 2, which results in reduction in the manufacturing cost of each individual semiconductor device.
Then, when the substrates 3 are consecutively formed in the substrate sheet material 2 as shown in FIG. 2A, after a semiconductor chips 4 are mounted to all the substrates of the substrate sheet material 2 as shown in FIG. 2C, the plurality of semiconductor chips 4 are collectively resin-molded as shown in FIGS. 3A and 3B, which results in a resin seal part 5 having a large area formed on the substrate sheet material 2. It should be noted that each of the substrates 3 formed in the substrate sheet material 2 has a semiconductor chip mounting portion 3a in the center portion thereof, as shown in FIG. 2B, and substrate side electrodes 3b, to which lead wires extending from electrodes of the semiconductor chips 4 are connected, are arranged in the vicinity of the circumference.
When the semiconductor chips 4 are of a flip-chip type, the substrate side electrodes are arranged corresponding to the electrodes of the semiconductor chips 4.
However, since a thermal expansion rate of the substrate sheet material 2 is different from that of a mold resin, a warp may occur in the substrate sheet material 2 after molding as shown in FIG. 4. Although it is effective to use a mold resin having a high glass transition temperature Tg in order to control generation of such a warp, the mold resin having a high glass transition temperature Tg is generally poor in a heat resistance, and, thus, a warp and a heat resistance are in a relationship of trade-off. Therefore, if an attempt is made to solve the problem of warping by the mold resin alone, there may be raised another problem that the reliability of a semiconductor device is decreased.
Such a warp of the substrate sheet material 2 is more remarkable as an area to be covered by molding is increased or the number of substrates to be molded is increased. Moreover, if a strip or rectangular material is used for the substrate sheet material, a degree of a warp increases in a direction along a longer side thereof.
Thus, in the present condition, the substrates 3 formed in the substrate sheet material 2 is divided into several groups as shown in FIG. 5, and molding is performed on an individual group basis as shown in FIGS. 6A and 6B. In the example shown in FIGS. 6A and 6B, the substrates 3 are divided into groups each including four pieces and resin molding is performed on each four substrates at one time so as to form a plurality of seal resin parts 6 each having an area smaller than that of the seal resin part shown in FIG. 3.
Thus, although a warp of the substrate sheet material 2 is suppressed by molding the substrates 3 by dividing them into groups, a number of substrates 3 formable in a single substrate sheet material 2 is decreased. This problem also occurs when increasing the number of substrates by increasing a size of the substrate sheet material 2, and is a bottle-neck for a more efficient manufacture of semiconductor devices.